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FITC1 Sigma

FluoroTag FITC Conjugation Kit

Synonym: FITC



Frequently Asked Questions

Frequently Asked Questions are available for this Product.

Analysis Note

1. Dissolve protein and FITC in carbonate-bicarbonate buffer.
2. Slowly add FITC to protein with stirring. Cover with foil and stir 2 hours at room temperature.
3. Separate conjugate from free FITC on G-25 column. Collect fractions.
4. Pool fractions containing conjugate.
5. Determine F/P ratio of conjugate spectrophotometrically.
6. Stabilize with 1% bovine serum albumin and 0.1% sodium azide and store at 0-5 °C.

Features and Benefits

• Suitable for both small (1 mg) and large (5 mg) scale conjugations
• Completely aqueous procedure - no DMF needed
• Fast gel filtration separation of conjugate from excess FITC
• Complete protocols for conjugation and F/P ratio determination
• Sufficient reagents for at least 5 conjugations of 5 mg protein each and for optimization of F/P ratio before scale-up
• References for applications and protocols


Sigma offers a convenient kit for preparing FITC-labeled antibodies. Fluorescein isothiocyanate (FITC), Isomer 1, is a widely used fluorophore, popular because of its high quantum efficiency and stability when conjugated. FITC is yellow-orange in color with an absorption maximum at 495 nm. Upon excitation it emits a yellow-green color with an emission maximum at 525 nm. Conjugation occurs through free amino groups of proteins or peptides, forming a stable thiourea bond (see reaction). FITC conjugates of antibodies, lectins, hormones, and growth factors have been used in a variety of immunohistochemical and flow cytometry applications. The protocols have been optimized for antibodies, but may be adapted to other proteins by the end user.


The Flourotag FITC Conjugation Kit can be used for Immunohistochemisty and Immunocytochemistry using Flow Cytometry. It is also be used for the conjugation of FITC to peptide hormones, cytokines, growth factors and proteins.

Legal Information

FluoroTag is a trademark of Sigma-Aldrich Co. LLC

Price and Availability

Amplified Detection

Kit component only


Product #

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0.1 M Carbonate-bicarbonate buffer capsule, pH 9.0 5 capsules SDS    

Standard component


Product #

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Fluorescein isothiocyanate isomer I, suitable for protein labeling, ≥90% (HPLC), powder 5 x 2 mg SDS F7250
Phosphate buffered saline, powder, pH 7.4, for preparing 1 L solutions 5 pkg SDS P3813
Sephadex G-25 column, 3.5 mL 1 SDS    
Sephadex G-25 column, 9.1 mL 1 SDS    
Safety & Documentation

Safety Information

GHS07  GHS07
Signal word 
Hazard statements 
Precautionary statements 
NONH for all modes of transport
Protocols & Articles


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